So I have not yet made my tutorial on how to do it, but there are two ways of doing it. If possible, the first way is the way that you want to do it, because that will keep the character's Final Smash eyes regularly, 100% chance. The second way, while having a chance of keeping the character's FS eyes, will not guarantee it, and it will also have certain glitches that the first way does not have. However, the second way can be used on ANY character, whereas the first way is limited to certain fighters.(Note: I will, after I make the tutorial, which is quite a long time from now, include a list of who the first way works on and who it does not, but that tutorial is a long ways off, currently, due to that it's currently school season)
Here are the two ways. Both methods start with the same process of opening up the model in BrawlBox, expanding the ModelData[0], expanding the MDL0, and expanding the Bones folder, and then the TopN bone. The next steps (per each of the two methods) are as follows:
Way #1:
Expand TransN, then expand XRotN. Select YRotN, and scroll down to "Scale"; edit these numbers to change the sizes. If you have difficulty with changing the numbers, you can let me know.
Way #2:
Rename EyeYellowM(Or whatever bone is immediately preceding TransN) to some other name. Right-click TransN and select "Add to Next Up". Select the bone that you just renamed, and scroll down to "Scale", and these numbers change the sizes. Again, if you have difficulty with changing the numbers, let me know.